Toxaphene is a persistent pesticide which is highly toxic to a broad range of organisms including freshwater fish. The sources of Toxaphene are still not clearly understood. Atmospheric transport from the cotton growing districts of the southeastern United States is presently considered the most plausible hypothesis. This mechanism, however, does not adequately explain all of the data on Toxaphene concentrations in different geographical regions of the U.S. In particular, concentrations in the immediate vicinity of the Great Lakes have been increasing, whereas decreases have been observed at Midwestern sites not near these lakes. It is conceivable that environmental chlorination reactions, not involving the manufacture or application of Toxaphene at all, may be generating materials closely related to or indistinguishable from Toxaphene. The objective of our research was to simulate pulp bleaching conditions in the laboratory and determine if Toxaphene-like materials could be produced. The aqueous chlorination of the monoterpenes, camphene, limonene, apinene and 8-pinene produced complex polychlorinated product mixtures. The extent of chlorination was primarily dependent on pH and light conditions. At pH 2 and exposed to sunlight product mixtures were obtained that had striking similarities to Toxaphene. At higher pH or in the dark, less extensive but still substantial chlorination took place; these lower chlorinated compounds could be mistaken for biologically degraded Toxaphene in environmental samples. We conclude that Toxaphene-like mixtures may conceivably be formed under environmental conditions, but the actual extent of formation of such mixtures and the degree to which they may contribute to apparent Toxaphene in natural samples remain to be assessed.